Foods have been smoked since humans first used fire to prepare meals. Smoking of foods has provided flavor, color, and preservation. Initially, preservation was the most critical reason to smoke foods, but as technology advanced, flavor and color have become the main reasons to smoke foods. As societies became more industrialized, the shift from home or individual smoking to processing in specialized plants led the need for better control of smoking procedures. Moreover, increased productivity drove the desire for more consistent smoke application techniques.
As a result, liquid smoke compositions (also known as liquid smoke solutions, and colloquially referred to as liquid smokes) were developed as a replacement for smoking of food by direct contact with smoke, and such compositions have become a standard industry practice. When applied to the surface of meats and other proteinaceous foodstuffs, such as various types of sausages, frankfurters, bolognas, beef rolls, hams, and the like, liquid smoke gives the item a characteristic smoke flavor and produces a dark smoked color. The achievement of a smokehouse-like product by application of an aqueous smoke solution to a foodstuff requires the control and balancing of many variables such as the food composition, temperature, humidity, processing time, contact time, amount of liquid smoke, and concentration of liquid smoke.
It is well known to those skilled in the art that liquid smoke compositions contain a wide array of chemical compounds, and over 400 such compounds have been identified. Nevertheless, it is also well known to those skilled in the art that liquid smoke compositions are characterized by their content of certain classes of compounds, namely, acids (% titratable acidity), phenols, and carbonyls.
The acids are preservatives, and, of course, pH control agents, as a result of which commercial liquid smoke compositions typically have a pH under about 2.5, and more typically under about 2.3, and a % titratable acidity by volume from about 3% to about 18%. The phenols give flavor, and also aroma, to liquid smoke compositions, and commercial compositions typically have a phenols content from about 3 to about 45, and more typically, from about 14 to about 30 mg/ml. The carbonyls impart the brown color to liquid smoke compositions. The phenols and the carbonyls can be measured as described in the below-mentioned U.S. Pat. No. 4,431,032 to Nicholson. The color-forming potential of liquid smoke compositions can be measured by the well-known Browning Index procedure described in the below-mentioned U.S. Pat. No. 4,994,297 to Underwood or by the well-known Staining Index procedure involving reaction of liquid smoke with glycine, as described below. It is noted that the acids and carbonyls are secondary in contributing to the flavor of liquid smoke compositions.
More specifically, liquid smoke was developed over 65 years ago, and is the aqueous condensate of natural wood smoke, as described in U.S. Pat. No. 1,753,358 issued in 1930 to Wright. Also, of interest in connection with older manufacturing procedures for liquid smoke is U.S. Pat. No. 2,400,466 issued in 1946 to Reiter et al.
Improved liquid smoke compositions and techniques for manufacture thereof are described in U.S. Pat. No. 3,106,473 to Hollenbeck, U.S. Pat. No. 3,873,741 to Melcer et al., U.S. Pat. No. 4,298,435 to Ledford, U.S. Pat. No. 4,154,866 to Dainius et al., and U.S. Pat. No. 4,994,297 to Underwood.
While the advent of liquid smoke compositions has significantly improved meat processing, attempts have been made over the last 20 years or so to deal with the tar problem of liquid smoke. Upon storage of a liquid smoke sticky, viscous precipitate on the bottom of the container for the liquid smoke.
Furthermore, although water is present in liquid smoke, it is not totally water soluble, which exacerbates the tar problem. More specifically, for commercial application of liquid smoke to a foodstuff, liquid smoke is typically diluted with water in an amount that results in 2 to 5 times the original volume of liquid smoke. However, the tar precipitate will also occur upon dilution of liquid smoke with water, and thus can easily be drawn into the piping of a system used in applying the liquid smoke to the foodstuff.
In connection therewith, it is noted that a liquid smoke composition and related process for maintaining the tar component of the liquid smoke in suspension so that the tar does not form undesirable solids during storage is described in U.S. Pat. No. 4,112,133 to Rao. More particularly, the patent to Rao is directed to admixing liquid smoke with a fatty compound, such as a polyoxyethylene sorbitan monooleate, a polyoxyethylene sorbitan monostearate, or a polyoxyethylene sorbitan monopalmitate to emulsify the tar.
Removing the tar instead of keeping it in emulsion is achieved by a solvent extraction process used on liquid smoke to create a desirable tar-depleted liquid smoke supernatant fraction and an undesirable tar-containing fraction, followed by gravity separation of the two fractions, as is described in U.S. Pat. Nos. 4,431,032, 4,431,033, and 4,496,595, all to Nicholson and in U.S. Pat. No. 4,592,918 to Chiu. Solvents such as dichloromethane or chloroform are used. Related thereto is the tar removal process described in U.S. Pat. No. 4,504,507 to Nicholson, wherein the pH of liquid smoke is raised above 4 to create a desirable tar-depleted liquid smoke supernatant fraction and an undesirable tar-containing fraction, followed by gravity separation of the two fractions.
The four patents to Nicholson also describe treating a surface of a food casing, such as a fibrous, cellulosic food casing used for sausages, with the tar-depleted liquid smoke. Furthermore, U.S. Pat. No. 5,288,532 to Juhl et al. describes a polymeric plastic film food casing, such as one made of a blend of ethylene vinyl acetate copolymer and polyethylene oxide, which during extrusion of the plastic film, has liquid smoke blended with the polymer beads. The liquid smoke then transfers, or bleeds out from the film, to the foodstuff packaged with the film.
Lastly, of interest in relation to removal of undesired components from liquid smoke is the process described in U.S. Pat. No. 4,959,232 to Underwood, which is directed to passing liquid smoke through a column of both ionic and non-ionic polymeric resin beads (suitable resins are copolymers of alkylacrylates and cross-linking polyvinylidene), or alternatively mixing the liquid smoke with the resin beads in a batch process, to remove flavor components thereof so that more of the resultant liquid smoke can be employed to impart more of the brown coloring to the treated foodstuff.
The disclosures of all of the above-mentioned patents are incorporated herein by reference.
Despite the above-discussed procedures to deal with removing or keeping suspended certain components of liquid smoke (such as removing tar by solvent extraction of liquid smoke or keeping tar in suspension by adding a sorbitan fatty compound to liquid smoke), nevertheless, problems still exist with such procedures. For instance, the solvent extraction process of the patents to Nicholson and the resin treatment process of the patent to Underwood both have a shortfall in that these processes leave residual solvents that are directly added by Nicholson or used by Underwood to condition the resin.
Keeping the tar suspended in accordance with the process of the patent to Rao requires addition of sorbitan fatty compounds which dilutes the liquid smoke, resulting not only in increased usage requirements but also impeding the color-forming reaction whereby the smoke can be rinsed away from the foodstuff if not properly set during application to the foodstuff. With this process, the tar is still in the liquid smoke so that the tar, as well as the added sorbitan fatty compound, is being eaten by the consumer of the smoke-treated foodstuff. Moreover, sorbitan fatty compounds have not been approved for application to foodstuffs in some countries, which limits the distribution of these smoke-treated foodstuffs.
Thus, it is desirable to find an improved liquid smoke composition that is tar-depleted and a method for the manufacture thereof, which composition and method obviate the above-mentioned problems.